Hydraulic press.



B. GERDAU.

HYDRAULIC PRESS.

APPLICATION FILED APR.28, 1909.

Patented Feb. 25, 1913.

2 SHEETS-SHEET 2.

L H r T TQ BAR'IHOLD GERDAU, 0F DUSSELDOBF GERMANY.

HYDRAULIC PRESS.

Specification of Letters Patent. Patented Feb. 25,

Application filed April 28, 1909. Serial No. 492,706.

To all whom it may concern:

Be it known that I, BARTHOLD GERDAU, engineer and manager, a subject of the German Empire, residing at Neanderstrasse l3, Dusseldorf, in the Kingdom of Prussia, Germany, have invented new and useful Improvements in Hydraulic Presses, of which the following is a specification.

The present invent-ion relates to improvements in hydraulic, or steam hydraulic, presses of that character or type in which an intensifying or pressure multiplying piston coiiperates with a primary or main pressing piston.

The object of the invention is to provide means by which it is possible to vary the relative positions of the main or primary pressing piston and the bed or part with which it cooperates without varying or effecting any adjustment of the intensifying or pressure multiplying piston.

ll ith this end in view the invention provides means by which there is maintained at all times in the cylinders of the primary or pressing piston and the return pistons a fluid pressure of such strength as to overbalance the inactive weight of the intensifying piston.

In the accompanying drawings, Figure 1 is a vertical sectional view through a press of the character referred to, constructed in accordance with the present invention, some of the parts being represented diagrammatically only; Fig. 2 is a similar view showing a slight modification.

Referring to the drawings and particularly to Fig. l A designates the primary or main pressing piston and B and C designate a pair of return pistons connected with the same cross head of the press as the primary piston. These parts may be of any ordinary and well known construction, each of such pistons working-within a suitable cylinder.

An intensifying or pressure multiplying piston N having its stem H extending into the cylinder of the primary piston A is arranged within a suitable cylinder having an inlet M for the admission of pressure fluid.

A fluid pressure reservoir E shown as a vessel for receiving liquid and air under pressure communicates through conduits D with the lower ends of the cylinders of the return pistons B, C, and the upper end of the cylinder of the main or primary piston A. An accumulatmor pressure creating device F is provided to maintain the desired pressure in the circulating system compris-i ing the reservoir E, the conduits D and the several piston cylinders referred to and to replace any fluid that may be Wasted by reason of leaks in such system.

A check valve G is arranged between the cylinder of the primary or main pressing piston A and the reservoir E so that the action of the intensifying or multiplying piston N H will not operate to force the pressure fluid from the cylinder of piston A to the reservoir and the cylinders of the pistons B and C.

From the foregoing description and the drawings it will be seen that movement of the pistons A, B, C, will eifect a movementof the pressure fluid through the conduits D and that such fluid will be maintained at a substantially constant pressure which as before noted is suflicient to overbalance the inactive Weight of the intensifying piston and maintain it stationary, when the pistons A, B, C, are adjusted or moved while the press inactive. Such adjustments of the parts referred to are effected by auxiliary pistons J K working in suitable cylinders shown as formed above and integrally cvith the cylinders of the return pistons B, C. The cylinders of the auxiliary pistons are connected with a pressure fluid system in which is arranged a valve L by manipulation of which the movement of said pistons can be readily controlled.

lVith the parts in the position shown in Fig. 1, if it is desired t'o-eifect an idle movement of the press or vary the position of the primary piston A while maintaining the intensifying piston N, H, stationary, the valve L is adjusted so that pressure fluid is admitted to the cylinders of the auxiliary pistons J, K, and the several pistons move downwardly. The pressure fluid .exj'iellcd from the cylinders of the return pistons B. i. will be caused to circulate through the iforesaid closed system and maintain the pressure in the cylinders of said pistons A. B, (l, practically constant, the only variations being negligible and in accordance with the relation of the dilfcrence. between the combined displacement of the pistons B and (l, and the piston A. to the air space in the reservoir E, the liquid flowing into or out of the reservoir as the pistons move. Adjustment of the valve l so that pressure fluid can pass from the cylinders of the 4 Lorraine auxiliary pistons J and K will permit upward movement of the pistons A, B, U, as

the operative area. of the return pistons is greater than that of the primary or pressing piston.

In the embodiment of the invention illustrated in Fig. 2, the auxiliary pistons J, K, operate by exerting a lifting instead of a depressing force, the inlets for the pressure fluid being at the lower ends of the cylinders for said pistons instead of adjacent the upper ends, as in the form shown in Fig. 1.

It will be seen that in both of the forms shown the liquid contained within the conduits D and the cylinders of the pistons A, B, C, is not acted upon or affected by any other liquid under pressure and the amount of such liquid remains constant except there be a leak. By varying the pressure in the. reservoir E the pressure exerted by said liquid can be changed so that the speed of the idle movements of the press will be regulated. The pressure-in such closed circulating system is always maintained high enough to insure that the intensifying piston will be returned to its initial position following each operation of the press and maintained at such position unafiected by any idle movement of the pressing piston.

What is claimed is:

1.7 In a press of the character referred to, the combination with a pressing piston, re-

turn pistons and an intensifying piston, of

means whereby, when the intensifying piston is'not in operation, said parts are maintainedu'ndera substantially constant pressure duringidle movements of the pressing piston,'said' pressure being of such strength as to hold the intensifying piston stationary.

'2. Ina press of the character referred to, the combination with a pressing piston, return pistons andan intensifying piston, of a circulating system including the cylinders of both said pressing and return pistons, and means for maintaining therein fluid under suflicient pressure to overbalance the inactive pressure of the intensifying piston, auxiliary pistons for edecting idle move ment of the pressing and return pistons, and fluid pressure means cont-rolling the action of the auxiliary pistons.

3. In a-press of the character referred to, the combination with a pressing piston, return pistons and an intensifying piston, of a fluid pressure reservoir connected with the cylinders of both the pressing and return pistons a check valve interposed between the cylinder of the pressing piston and said reservoir, a pair of auxiliary pistons connected with the return pistons, cylinders for said auxiliary pistons, means for supplyin pressure fluid to the cylinders of the auxi iary pistons, and a valve controllingrthe admission and escape of such fluid om the cylinders of the auxiliary pistons and adapted to open the check valve between the reservoir and the cylinder of the pressing piston, substantially as and for the purpose scribed.

4:. In a press of the character referred to, the combination with a pressing piston, a return piston, an intensifying piston and the cylinders therefor, of pressure supply means, conduits connecting said pressing and return piston cylinders with said supply means and so arranged as to provide a substantially constant pressure in said cylinders and permit the working fluid to circulate freely from one cylinder to another, as the pistons are moved, when the intensifying piston is inactive, and means for preventing the working fluid from passing from the cylinder of the pressing piston to the cylinder of the return piston when the intensifying piston is active.

BARTHOLD GERDAU. [Ls] Witnesses:

()rro Kom'o, WILLY IiIEIN. 

